Recovery and Delay of Impurity-Induced Poisoning of Oxygen Exchange Kinetics in Mixed Conducting Oxides Via Controlled Surface Acidity

Abstract

The oxygen exchange kinetics in mixed conducting oxide surfaces are critical to a variety of energy-related technologies, including solid oxide fuel/electrolyzer cells (SOFCs/SOECs), permeation membranes, batteries, and sensors. Such devices, however, commonly suffer from performance degradation from impurity-poisoning during long-term operation. In our previous findings, it was found that while acidic additives can depress the surface exchange kinetics, basic additives can enhance these kinetics. Inspired by these findings, we demonstrated the ability to regenerate acidic (Cr and Si)-poisoned surfaces by compensating with basic additive infiltrants (Li and Ca). Electrical conductivity relaxation measurements on porous mixed conducting oxide specimens were used to examine the impact of infiltrants on the oxygen exchange rate coefficient (kchem ) and revealed that the recovery of poisoned surface kinetics can be attributed to the compensation of depleted surface electrons by basic additives.